Whenever I export my layout to a PDF, the labels don't show up. They're not in a separate label layer or anything, they're just simply labeled features. I'm using ArcGIS Pro 2.6. I'm new to Pro - is there some sort of option I need to switch on to get the labels to show when the map is exported as a PDF?
I've tested exporting to a JPG and the labels export fine that way.
Edit: I tested printing to a PDF and it worked. So exporting to a PDF must just be a bug?
I will admit I've seen quite a few export issues arise in 2.6. However many of them were alleviated in 2.6.1 so I would recommend upgrading to see if that helps. I looked into our internal systems for an issue similar to yours and didn't find anything upon my initial searches. Before proceeding with the upgrade to 2.6.1 there are a couple things you can try. Convert the labels to annotations and attempt the export again. You will find this option by right clicking the layer in question and the option will be just below the Labeling Properties button. This essentially creates a new layer for the labels and treats each label as its own individual feature, allowing for advanced editing capabilities. Although that is not the purpose for which we are using it here, it is still worth a shot.
Another quick test you could try would be to switch the labeling engine. By default this should be set to the Maplex Labeling engine, however you can use the Standard Labeling engine and see if there is a different result. This can be done by highlighting the feature layer in question within the Contents pane then hit the Labeling tab at the top. On the very right side of this ribbon within the Map group these is a More button. Click this and uncheck the "Use Maplex Labeling Engine" option. Try the export again after doing this.
I hope this helps!